Surfactant--polymer aggregates formed by sodium dodecyl sulfate, poly(N-vinyl-2-pyrrolidone), and poly(ethylene glycol)

Polyelectrolyte–Dye Interactions: An Overview

Polyelectrolytes are polymers with repeating units of ionizable groups coupled with counterions. Recently, polyelectrolytes have drawn significant attention as highly promising macromolecular materials with potential for applications in almost every sector of our daily lives. Dyes are another class of chemical compounds that can interact with substrates and subsequently impart color through the selective absorption of electromagnetic radiation in the visible range. This overview begins with an introduction to polyelectrolytes and dyes with their respective definitions, classifications (based on origin, molecular architecture, etc.), and applications in diverse fields. Thereafter, it explores the different possible interactions between polyelectrolytes and dyes, which is the main focus of this study. The various mechanisms involved in dye–polyelectrolyte interactions and the factors that influence them are also surveyed. Finally, these discussions are summarized, and their future perspectives are presented.

Impacts of polyols and temperature on the micellization, interaction and thermodynamics behavior of the mixture of tetradecyltrimethylammonium bromide and polyvinyl alcohol

Herein, the aggregation manner of the mixture of polyvinyl alcohol (PVA) and tetradecyltrimethylammonium bromide (TTAB) was performed in polyols (glucose, maltose and galactose) media over 300.55–320.55 K temperatures range with 5 K interval through conductivity measurement method. The micelle formation of TTAB + PVA mixture was identified by the assessment of critical micelle concentration (CMC) from the plots of specific conductivity (κ) versus TTAB concentration. The degree of micelle ionization (α), the extent of bound counter ions (β) as well as thermodynamic properties ( Δ G m 0 ${\Delta}{G}_{m}^{0}$ , Δ H m 0 ${\Delta}{H}_{m}^{0}$ and Δ S m 0 ${\Delta}{S}_{m}^{0}$ ) of TTAB + PVA systems have been estimated. The CMC values reveal that the micelle formation of TTAB + PVA mixture experience an enhancement in the manifestation of polyols. The values of free energy of micellization ( Δ G m 0 ${\Delta}{G}_{m}^{0}$ ) are negative for the TTAB + PVA system in aqueous polyols media, suggesting a spontaneous aggregation phenomenon. The Δ H m 0 ${\Delta}{H}_{m}^{0}$ and Δ S m 0 ${\Delta}{S}_{m}^{0}$ values of TTAB + PVA systems direct that the PVA molecule interacts with TTAB through the exothermic, ion-dipole, and hydrophobic interactions. The thermodynamic properties of transfer were also determined for the move of TTAB + PVA mixture from H2O to water + polyols mixed solvents. The values of compensation temperature (T c) and intrinsic enthalpy gain ( Δ H m 0 , ∗ ${\Delta}{H}_{m}^{0,\ast }$ ) were evaluated and discussed for the studied system.

Synthesis and Properties of Octadecyl Trimethyl Ammonium Polyacrylic Surfactants

In order to expand the application range of surfactants, octadecyl trimethyl ammonium chloride (OTAC) and polyacrylic acid (PAA) were used as raw materials to synthesize octadecyl trimethyl ammonium polyacrylic (OTAP). The molar ratios of OTAC to polyacrylic acid monomer were 1:1, 1:2 and 1:3. The synthesized compounds were named as OTAP-1, OTAP-2, OTAP-3. The obtained research results show that the best foaming ability was achieved with OTAP-1, and the best foam stability with OTAP-2. When the concentration was 2.0 g/L, the order of the emulsifying ability was: OTAP-1 > OTAP-2 > OTAP-3; when the concentration was 4.0 g/L, the emulsifying ability order was OTAP-2 > OTAP-3 > OTAP-1. OTAP-1 had a corrosion inhibition capacity of up to 85.11 %, and OTAP-2 and OTAP-3 had a sustained release rate of 81.06 % and 72.82 %, respectively. OTAP-3 had a good effect on scale inhibition, and the scale inhibition rate was 65.01 %.

Investigation of pseudo-polyanion formation between polyvinylpyrrolidone and sodium dodecanoate in aqueous solution by capillary electrophoresis, conductometry, tensiometry and calcium stability

H-bonding replaces sodium bridging in the PVP–SD complexation with pH reduction.

Modulation of partition and localization of perfume molecules in sodium dodecyl sulfate micelles

The influence of perfume molecules on the self-assembly of the anionic surfactant sodium dodecyl sulfate (SDS) and their localization in SDS micelles have been investigated by ζ potential, small angle X-ray scattering (SAXS), one- and two-dimensional NMR and isothermal titration microcalorimetry (ITC). A broad range of perfume molecules varying in octanol/water partition coefficients P are employed. The results indicate that the surface charge, size and aggregation number of the SDS micelles strongly depend on the hydrophobicity/hydrophilicity degree of perfume molecules. Three distinct regions along the log P values are identified. Hydrophilic perfumes (log P < 2.0) partially incorporate into the SDS micelles and do not lead to micelle swelling, whereas hydrophobic perfumes (log P > 3.5) are solubilized close to the end of the hydrophobic chains in the SDS micelles and enlarge the micelles with higher ζ potential and a larger aggregation number. The incorporated fraction and micelle properties show increasing tendency for the perfumes in the intermediate log P region (2.0 < log P < 3.5). Besides, the molecular conformation of perfume molecules also affects these properties. The perfumes with a linear chain structure or an aromatic group can penetrate into the palisade layer and closely pack with the SDS molecules. Furthermore, the thermodynamic parameters obtained from ITC show that the binding of the perfumes in the intermediate log P region is more spontaneous than those in the other two log P regions, and the micellization of SDS with the perfumes is driven by entropy.

Interaction of cationic gemini surfactant tetramethylene-1,4-bis(dimethyltetradecylammonium bromide) with anionic polyelectrolyte sodium carboxymethyl cellulose, with two different molar masses, in aqueous and aquo-organic (isopropanol) media

Interactions of the cationic gemini surfactant, 14-4-14 with anionic polymer, NaCMC.

Physicochemical behaviors of cationic gemini surfactant (14-4-14) based microheterogeneous assemblies

A comprehensive study of micellization and microemulsion formation of a cationic gemini surfactant (tetramethylene-1,4-bis(dimethyltetradecylammonium bromide; 14-4-14) in the absence or presence of hydrophobically modified polyelectrolyte, sodium carboxymethylcellulose (NaCMC), has been conducted by conductometry, tensiometry, microcalorimetry, and fluorimetry methods at different temperatures. Both critical micelle concentration and degree of ionization of the surfactant have been observed to increase with increasing temperature. The interfacial and thermodynamic parameters were evaluated. The standard Gibbs free energy of micellization (ΔGm°) is negative, which decreases with increase in temperature. Larger entropic contribution is observed compared to the enthalpy. The interaction of 14-4-14 with NaCMC produces coacervates which was determined from turbidimetry method. The pseudoternary phase behavior of the microemulsion systems comprising water (or NaCMC as additive), 14-4-14, isopropanol (IP) or n-butanol (Bu) as cosurfactant, and isopropyl myristate (IPM) were studied at 298 K. Phase diagrams reveal that IP derived microemulsions (in the absence of NaCMC) offer a large isotropic region compared to Bu-derived systems at comparable physicochemical conditions. Increasing the concentration of IP or Bu decreases the isotropic region in the phase diagram. NaCMC influences the microemulsion zone, depending upon its concentration, and type of cosurfactant and surfantant/cosurfactant ratio. Dynamic light scattering and conductometric measurements show the size of the droplet, threshold temperature of percolation, scaling parameters, and activation energy of the percolation process of 14-4-14/IP or Bu derived microemulsion systems without/with NaCMC at various physicochemical conditions. Bu exerts a greater effect to reduce θt than IP as a cosurfactant (in the absence of NaCMC) at comparable ω. On the other hand, IP showed better percolating effect than Bu in the presence of NaCMC. Bu and IP (as cosurfactant) and NaCMC (as additive) influenced the microemulsion droplet size (Dh) to different extents under comparable conditions. Temperature insensitive microemulsions have been reported at the studied temperature range (298–353 K). 14-4-14/IP (1:2)-derived microemulsion showed a fractured surface at fixed ω = 15, where ω is the water and surfactant molar ratio, and temperature (298 K); whereas, large scale mesospheres comprising multiple closely winded nanoslices and spheroid morphology were formed in 14-4-14/IP and 14-4-14/Bu microemulsions, respectively, in the presence of 0.01 g % NaCMC, at comparable conditions. These systems revealed good antimicrobial activity toward the strains of Gram-positive Bacillus subtilis and Gram-negative Escherichia coli bacteria at 298 K, and inhibitory effect was governed by ω, type of cosurfactant, and bacterial strains.

Experimental study on dynamic interfacial tension with mixture of SDS-PEG as surfactants in a coflowing microfluidic device

In this work, a coflowing microfluidic device was used to determine the influence of different mixed sodium dodecyl sulfate (SDS)-poly(ethylene glycol) (PEG) compound systems on dynamic interfacial tension and, by extension, corresponding emulsion droplet sizes. The aqueous solutions were used as the continuous phase in the microfluidic device, while octane was used as the organic dispersed phase. Combined SDS-PEG systems lower the interfacial tension more than either component can alone up to the critical aggregation concentration (CAC) of SDS. Octane droplet sizes produced in the microfluidic device using combined SDS-PEG systems were smaller than those produced using SDS alone, and a reduction in dynamic interfacial tension as determined by drop size followed a pattern similar to that observed in the static case (PEG4000 > PEG600 > PEG400 > PEG200 > PEG8000) with the exception of PEG8000. Finally, a previously formulated model relating interfacial tension to droplet size was used to estimate the dynamic interfacial tensions in the microfluidic device.

A comparative study of polyelectrolyte induced metachromasy

The interaction of two cationic dyes, namely crystal violet (CV), with anionic polyelectrolytes, namely sodium carrageenate (NaCar) and sodium heparinate (NaHep), has been investigated by spectrophotometric method. The polymers induced metachromasy in the dye resulting in the shift of the absorption maxima of the dyes towards shorter wavelengths. The stability of the complexes formed between crystal violet and sodium carrageenate was found to be greater than that formed between crystal violet and sodium heparinate. This fact was further confirmed by reversal studies using alcohols, urea surfactants and electrolytes. The interaction parameters revealed that binding between crystal violet and sodium carrageenate was mainly due to electrostatic interaction while that between crystal violet and sodium heparinate is found to involve both electrostatic and hydrophobic forces.

A study of interaction of cationic dyes with anionic polyelectrolytes

The interactions of Acridine Orange with Sodium Alginate and Pinacyanol Chloride with Heparin have been investigated by spectrophotometric method. The polymers induce metachromasy in the dye as evidenced from the considerable blue shift in the absorption maxima of the corresponding dyes. The interaction constant and thermodynamic parameters of polymer-dye interactions have been determined. The effect of additives such as alcohols, and urea on the reversal of metachromasy has been studied. The data has been used to determine the stability of the metachromatic complex and the nature of binding. The thermodynamic parameters of interaction revealed that binding between Acridine Orange and Sodium Alginate involved only electrostatic forces while that between Pinacyanol Chloride involved both electrostatic and hydrophobic forces. The reversal studies using surfactants indicated the involvement of both electrostatic and hydrophobic forces in binding. Based on the results it can be concluded that Pinacyanol Chloride is more effective inducing metachromasy than Acridine Orange.

A comparative study of polyelectrolyte-dye interactions

The interaction of Azure B with sodium alginate and heparin in aqueous solution has been studied by spectrophotometric method. Absorbance of Azure B at 645 nm decreases and a new band appeared at 545 nm and at 556 nm respectively which indicated that a new metachromatic complex formed. A linear decrease in absorbance is noted. It was found that sodium alginate is more effective than heparin in decreasing the absorbance of Azure B at 645 nm. The stoichiometry of sodium alginate or heparin with Azure B was determined by spectrophotometry. The results suggested that the interaction between Azure B with sodium alginate or heparin was a result of electrostatic forces and the difference between heparin and sodium alginate were attributed to the different negative charge number on repetitive disaccharides unit. Studies on the effect of alcohol or urea indicated that sodium alginate and heparin interacted with the aggregates of Azure B. Thermodynamic parameters of interaction has been evaluated to determine the stability of the metachromatic complex. The effect of surfactants on reversal of metachromasy has also been studied.

Effects of surfactants and electrolytes on adsorbed layers and particle stability

Adsorbed polymer and polyelectrolyte layers on colloidal silica nanoparticles have been studied in the presence of various salts and surfactants using photon correlation spectroscopy and solvent relaxation NMR. Poly(ethylene oxide) (PEO; molar mass 103.6 kg mol (-1)) adsorbed with a relatively high affinity and gave a layer thickness of 4.2 +/- 0.2 nm. While the nonionic surfactant used only increased this thickness slightly, anionic surfactants had a much greater effect, mainly due to repulsions between adsorbed aggregates, leading to expansion of the layer. A nonionic/anionic surfactant mixture was also tested and resulted in a larger increase in layer thickness than any of the individual surfactants. The dominant factor on addition of salt was generally the reduced solvency of PEO, which resulted in a further increase in the layer thickness but in some cases caused flocculation. This was not the case when the surfactant was sodium dodecylbenzenesulfonate; instead screening of the intermicellar repulsions possibly combined with surfactant-cation binding resulted in a reduction in the layer thickness. In comparison the affinity between silica and sodium polystyrenesulfonate was very weak. Anionic surfactants and salts did not noticeably increase the strength of adsorption, but instead encouraged flocculation. The situation was different with a nonionic surfactant, which was able to adsorb to silica itself and apparently facilitated a degree of polyelectrolyte adsorption as well.

Physicochemical Studies on Pepsin−CTAB Interaction: Energetics and Structural Changes

The interaction between pepsin and CTAB has been elaborately studied with a number of techniques. The enzyme-induced interaction produced complexes, aggregates, and micelles of CTAB with distinct physicochemical features. It was found that at very low surfactant concentration (much below the critical micellar concentration (cmc) of pure CTAB), the surfactant got adsorbed both in monomeric and lower aggregated forms to the high-energy sites of the native biopolymer, leading to enhanced hydrophobicity of the combine, and hence, lowering of the interfacial (air/solution) tension. This was followed by the formation of a faintly turbid solution of the polymer-surfactant coacervate. The CTAB interacted unfolded pepsin along with the surfactant monomer remained adsorbed at the interface to decrease the interfacial tension (gamma) to a low level to produce a break in the gamma vs log [CTAB] plot prior to the normally observed extended cmc (cmce) in presence of polymers. The cac-like aggregation (as observed in tensiometry and viscometry) was not found in conductometry and microcalorimetry, whereas microcalorimetry evidenced the formation of the cmce of CTAB in the presence of the biopolymer. The CTAB influenced structural features of the pepsin were assessed from spectral, viscometric, and circular dichroism measurements.

Influence of a surfactant and electrolytes on adsorbed polymer layers

Solvent relaxation NMR and small-angle neutron scattering have been used to characterize adsorbed poly(ethylene oxide) (PEO) layers on silica at a range of surfactant and electrolyte concentrations. Below the critical aggregation concentration (cac), the results suggest that sodium dodecyl sulfate (SDS) interacts relatively weakly, perhaps analogously to a simple salt reducing the solvency of PEO. This is evidenced by a decrease in the adsorbed layer thickness combined with an increase in the bound fraction, although the total adsorbed amount is not greatly affected. The layer thickness goes through a minimum at the cac, after which further SDS addition results in the formation of PEO/SDS aggregates that repel each other and, hence, tend to desorb. The adsorbed amount therefore decreases, from 0.7 mg m(-2) initially to 0.2 mg m(-2) with 32 mM SDS. The aggregates that remain adsorbed also repel, and hence, there is an increase in the layer thickness and the persistence length, while the bound fraction is reduced. In comparison, the effects of electrolyte at the ionic strength studied are relatively minimal. There is, however, evidence that the repulsions between adsorbed PEO/SDS aggregates are partially screened, allowing them to approach each other more readily. This leads to a contraction of the adsorbed layer when the SDS concentration is sufficiently high.

Study of the interaction between Apis mellifera venom and micro-heterogeneous systems

The bee venom, used in treatment of inflammatory and articular diseases, is a complex mixture of peptides and enzymes and the presence of tryptophan allows the investigation by fluorescence techniques. Steady state and time-resolved fluorescence spectroscopy were used to study the interaction between bee venom extracted from Apis mellifera and three micro heterogeneous systems: sodium dodecylsulphate (SDS) micelles, sodium dodecylsulphate-poly(ethylene oxide) (SDS-PEO) aggregates, and the polymeric micelles LUTROL F127, formed by poly(ethylene oxide)-poly(propylene oxide)- poly(ethylene oxide). Fluorescence parameters in buffer solution were typical of peptides containing tryptophan exposed to the aqueous medium, and they gradually changed upon the addition of surfactant and polymeric micelles, demonstrating the interaction of the peptides with the micro heterogeneous systems. Quenching experiments were carried out using the N-alkylpyridinium ions (ethyl, hexyl, and dodecyl) as quenchers. In buffer solution the quenching has low efficiency and is independent of the alkyl chain length of the quencher. In the presence of the micro heterogeneous systems the extent of static and dynamic quenching enhanced, showing that both fluorophore and quenchers reside in the microvolume of the aggregates. The more hydrophobic quencher (dodecyl pyridinium ion) provides higher values for K (SV) and dynamic quenching constants, and SDS-PEO aggregates are most efficient to promote interaction between peptides and alkyl pyridinium ions. The results proved that bee venom interacts with drug delivery micelles of the copolymer LUTROL F127.